[Bug c/48091] No warning when given function arguments mismatch earlier function definition which GCC assumes to be K&R

[eerott at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48091

Eero Tamminen <eerott at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|No warning when given       |No warning when given
                   |function arguments mismatch |function arguments mismatch
                   |earlier, old style K&R      |earlier function definition
                   |function definition         |which GCC assumes to be K&R

--- Comment #3 from Eero Tamminen <eerott at gmail dot com> 2011-03-30 17:59:26 UTC ---
Another example about how dangerous this default GCC behavior is.

Consider code A:
------------------
static int a, b;

void set_a(int i) {
        a = i;
}
void set_b(int i) {
        b = i;
}
int add() {
        return a+b;
}
------------------

And its usage from elsewhere:
------------------
#include <stdio.h>
int main(int argc, const char *argv[] __attribute__((unused)))
{
        return add(argc, 50);
}
------------------

GCC doesn't catch this because it assumes the code is obsolete K&R syntax
without even bothering to give user a warning about it.  Even when user is
requesting warnings with options like:
  gcc -Wall -Wextra --std=c99 -pedantic -O2 test.c

Code A) is *not* K&R.  Nowadays it's either C++ code copied to a C program or
code from people who don't know or remember that only in C++ "add()" means void
argument whereas in ANSI-C "add(void)" should be used.

I see this in (non-K&R) C sources all the time, it's very common mistake about
which GCC doesn't bother to give any warning.

Confirmed?